1. Field of the Invention
This invention concerns a cloth feed mechanism for sewing machines and, more specifically, it relates to an upper feed dog mechanism that moves in four directions on or above the upper surface of a cloth interlocked with the mechanism of the sewing machine for feeding the cloth.
2. Description of the Prior Art
The conventional upper feed dog mechanism of this type is designed to move in four directions in cooperation with a lower feed dog mechanism having a main feed dog and a sub feed dog in such a way that is descends when the main and sub feed dogs rise and vice versa, that is, with an opposite phase in its vertical movement to that in the vertical movement of the main and sub feed dogs. Further, the main and sub feed dogs and the upper feed dog are operationally related to the vertical movement of a needle such that when each of the feed dogs separates from the cloth downwardly or upwardly to complete the cloth feeding, the needle is inserted into the cloth; and when the needle leaves the cloth, each of the feed dogs move upwardly or downwardly to feed the cloth in contact therewith. Furthermore, as disclosed in Japanese Patent Application No. 92329/1979 and in Japanese Patent Laid-Open Publication No. 25149/1978, the upper feed dog is fixedly supported to a top end of an upper feed arm that moves in four directions interlocked with the mechanism of the sewing machine.
Such a mechanical arrangement, however, has several drawbacks. For instance, since the upper feed dog presses the upper surface of the cloth when the needle disengages from the cloth and the needle is inserted into the cloth when the upper feed dog rises from the cloth, it is impossible to remove the cloth during the sewing work from the sewing area. Further, since the upper feed dog is always situated near the sewing area and cannot be moved to another position separated therefrom, the upper feed dog interferes with such work as exchanging the needle, threading the needle or removing thread entangled in the sewing area or the looper due to thread disconnection and the working efficiency is reduced.